There exists a voluminous body of both patent and nonpatent literature describing agglomeration processes for producing a wide variety of dry, pourable, particulate detergent products whose formulations are based, in the main, on particulate hydratable detergent salts. Although these agglomeration processes may vary procedurally, one from the other, one step common to all is a liquid-solid blending step to effect agglomeration of all the solid components in the detergent formulation and to induce hydration of the hydratable detergent salts present therein.
A major objective of detergent manufacturers is the production of detergent products which are characterized by good storage stability, i.e., are resistant to caking, at ambient temperatures. Thus, a second step common to all agglomeration processes is the aging of the agglomerated and hydrated detergent formulations. This aging is carried out under relatively mild temperature conditions and for a period of time sufficient to remove excess free (or nonbound) water and to convert the hydratable detergent salts in the detergent formulation to their stable hydrates.
While the above generally described agglomeration processes work well for preparing most detergent products based on detergent formulations containing hydratable detergent salts, it has been observed that these processes do not work well on detergent formulations which also contain certain commonly employed hardness sequestering agents. Particularly, it has been observed that when hardness sequestering agents such as alkali metal salts of aminopolycarboxylic acids are incorporated into detergent formulations containing hydratable detergent salts and this formulation subsequently agglomerated and aged, the resulting particulate detergent product obtained lacks the requisite storage stability required of present day detergent products.
The present invention is based upon the surprising discovery of a new process which provides for the agglomeration of particulate, substantially hydrated detergent products from detergent formulations incorporating alkali metal salts of aminopolycarboxylic acids which detergent products are characterized by their excellent storage stability.